1. Field of the Invention
The present invention relates generally to the field of vehicle suspension systems and, more particularly, to a vehicle height control system.
2. Description of the Prior Art
A conventional vehicle height control system, which is disclosed in U.S. Pat. No. 4,537,411, includes four sensors, each of which detects the height between a rotating center of an associated wheel and a vehicle body, four suspension devices each of which is disposed between a rotating center of an associated wheel and the vehicle body, a pressure source connected to the suspension devices, four valves, each of which is disposed between each suspension device and the pressure source, and a control means in the form of a program controlled microcomputer.
In the conventional vehicle height control system, the control means manipulates each valve so as to control the fluid communication between the pressure source and each suspension device when a sensor detects an excess height variation so that the height of the vehicle is adjusted within a predetermined range.
However, during each of the following possible vehicle operating conditions, the conventional vehicle height control system unnecessarily adjusts the vehicle height:
(1) A vehicle is being parked with its engine operating in such a manner that any one of the wheels is inadvertently run onto the sidewalk which is considerably higher than a road surface. PA0 (2) A body of a vehicle is jacked-up with the jack positioned near any of the wheels which are in rotation, for example, in a service shop. PA0 (3) Any one of the wheels has fallen into a gutter or a pothole along a road and the engine is operating.